Tutorial by Examples: le

Optimizing by executing less code

The most straightforward approach to optimizing is by executing less code. This approach usually gives a fixed speed-up without changing the time complexity of the code. Even though this approach gives you a clear speedup, this will only give noticable improvements when the code is called a lot. R...

C++ • Optimization in C++

Creating and editing session variables that are arrays

Save the session variable as a variable. $session = Yii::$app->session; $sess = $session['keys']; Then create or update the array value you want $sess['first'] = 'abc'; And finally save to the session variable $session['keys'] = $sess

yii2 • Session

match? - Boolean Result

Returns true or false, which indicates whether the regexp is matched or not without updating $~ and other related variables. If the second parameter is present, it specifies the position in the string to begin the search. /R.../.match?("Ruby") #=> true /R.../.match?("Ruby&quot...

Ruby Language • Regular Expressions and Regex Based Operations

Create .NET Core "Hello World" console project

Create a new project.json and example Program.cs: dotnet new Restore needed packages: dotnet restore Compile and run the example: dotnet run

.net-core • .NET Core command line interface

ListView in AlertDialog

We can always use ListView or RecyclerView for selection from list of items, but if we have small amount of choices and among those choices we want user to select one, we can use AlertDialog.Builder setAdapter. private void showDialog() { AlertDialog.Builder builder = new AlertDia...

Android • Dialog

Creating a hash table

Hash tables are created by make-hash-table: (defvar *my-table* (make-hash-table)) The function may take keyword parameters to further specify the behavior of the resulting hash table: test: Selects the function used to compare keys for equality. Maybe a designator for one of the functions eq,...

common-lisp • Hash tables

Iterating over the entries of a hash table with maphash

(defun print-entry (key value) (format t "~A => ~A~%" key value)) (maphash #'print-entry *my-table*) ;; => NIL Using maphash allows to iterate over the entries of a hash table. The order of iteration is unspecified. The first argument is a function accepting two parameters: ...

common-lisp • Hash tables

Map and Filter Over A Collection

Map 'Mapping' across a collection uses the map function to transform each element of that collection in a similar way. The general syntax is: val someFunction: (A) => (B) = ??? collection.map(someFunction) You can provide an anonymous function: collection.map((x: T) => /*Do something wi...

Scala Language • Collections

Using Single Slots

Single slots are used when a child component only defines one slot within its template. The page component above uses a single slot to distribute content. An example of the page component's template using a single slot is below: <html> <head> <title>Page Title</t...

Vue.js • Slots

Namespace variables

The variable command ensures that a given namespace variable is created. Until a value is assigned to it, the variable's value is undefined: namespace eval mynamespace { variable alpha set alpha 0 } The variable can be accessed from outside the namespace (from anywhere, in fact) by at...

tcl • Variables

Check matching fields in two files

Given these two CSV files: $ cat file1 1,line1 2,line2 3,line3 4,line4 $ cat file2 1,line3 2,line4 3,line5 4,line6 To print those lines in file2 whose second column occurs also in the first file we can say: $ awk -F, 'FNR==NR {lines[$2]; next} $2 in lines' file1 file2 1,line3 2,line4...

awk • Two-file processing

Gradle Parallel builds

Gradle will only run one task at a time by default, regardless of the project structure. By using the --parallel switch, you can force Gradle to execute independent subprojects - those that have no implicit or explicit project dependencies between one another - in parallel, allowing it to run multip...

gradle • Gradle Performance

Use latest Gradle version

The Gradle team works regularly on improving the performance of different aspects of Gradle builds. If you’re using an old version of Gradle, you’re missing out on the benefits of that work. Try upgrading to the latest version of Gradle to see what kind of impact it has. Doing so is low risk because...

gradle • Gradle Performance

Split routes into multiple files

If your routes file is overwhelmingly big, you can put your routes in multiple files and include each of the files with Ruby’s require_relative method: config/routes.rb: YourAppName::Application.routes.draw do require_relative 'routes/admin_routes' require_relative 'routes/sidekiq_routes' ...

Ruby on Rails • Routing

Core Extensions: String Inflection

String#pluralize Returns of plural form of the string. Optionally takes a count parameter and returns singular form if count == 1. Also accepts a locale parameter for language-specific pluralization. 'post'.pluralize # => "posts" 'octopus'.pluralize # => &quot...

Ruby on Rails • ActiveSupport

Minimal Chart Example

Depending on the version of Chart.JS you are using (the current one being 2.X), the syntax is different to create a minimal example of a bar chart (JSFiddle Demo for 2.X). Chart.js 2.X <html> <body> <canvas id="myChart" width="400" height="400&...

chart.js • Getting started with chart.js

Natural (comparable) vs explicit (comparator) sorting

There are two Collections.sort() methods: One that takes a List<T> as a parameter where T must implement Comparable and override the compareTo() method that determines sort order. One that takes a List and a Comparator as the arguments, where the Comparator determines the sort order. ...

Java Language • Comparable and Comparator

Optimization Example (golden)

The 'Golden' method minimizes a unimodal function by narrowing the range in the extreme values import numpy as np from scipy.optimize import _minimize from scipy import special import matplotlib.pyplot as plt x = np.linspace(0, 10, 500) y = special.j0(x) optimize.minimize_scalar(special.j0,...

scipy • How to write a Jacobian function for optimize.minimize

Optimization Example (Brent)

Brent's method is a more complex algorithm combination of other root-finding algorithms; however, the resulting graph isn't much different from the graph generated from the golden method. import numpy as np import scipy.optimize as opt from scipy import special import matplotlib.pyplot as plt ...

scipy • How to write a Jacobian function for optimize.minimize

Creating an array of variables

$username = 'Hadibut'; $email = '[email protected]'; $variables = compact('username', 'email'); // $variables is now ['username' => 'Hadibut', 'email' => '[email protected]'] This method is often used in frameworks to pass an array of variables between two components.

PHP • Arrays